 STOP 2 - TRIP TWO
(Next Stop) (Previous Stop) (Index Map) (Trip 2 Home) (Trip 1 Home) Conocheague - Late Cambrian Geology 364 - Stratigraphy and Basin Analysis Dept. of Geology and Environmental Studies James Madison University Lynn S. Fichter
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STOP 2 - TRIP TWO
(Next Stop) (Previous Stop) (Index Map) (Trip 2 Home) (Trip 1 Home) Conocheague - Late Cambrian Geology 364 - Stratigraphy and Basin Analysis Dept. of Geology and Environmental Studies James Madison University Lynn S. Fichter
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The Conococheague is a formation with lots of wonderfully developed carbonate tidal features, some illustrated to the right and below. To the right is Algal laminated ribbon rock. The distinct layering are the algal laminates. In between are tan dolomite layers that are the ribbon rock nature. This block also had prism cracks in it.
Pelmicrite with some small interclasts (the thin, elongate dark gray streaks). Pellets (fecal pellets) are very common in this formation. It is probably more proper to refer to them as "pellatoids" since it is not clear they are not also oolites. In thin section they are too recrystallized to determine. 
Flat Pebble Conglomerate (Intraformational Conglomerate) in the lower bed; note the light gray chips oriented various ways. These form from mud crack chips that dessicate enough to separate from the underlying substrate. They then get caught up in the tidal currents and eventually deposited in tidal channels.
Herringbone Cross Bedding in pelletal limestone, partially pressure solutioned to produce white streaks along the foresets. Herringbone cross bedding is diagnostic of tidal currents where the current first flows one way on the flood tide, and then back the other on the ebb tide. The sand bars are typically found in lower intertidal channels or in subtidal sand bars. These are especially nice examples that cover several times more area than seen in the picture.
Ribbon rock is pervasive in lower intertidal and subtidal environments. The light gray is micrite, the tan the dolomitic ribbon. Ribbon rock is a pressure solution feature; i.e. noise.
Stromatolites are common in the Conococheague. Note the mound shape just above the middle of the picture (the light was bad for taking pictures so the images are not always the best). Sometimes they are completely replaced by chert, at other times they are still mostly carbonate. Although this picture does not show it, just down the bed there is a lot of chert replacement.
